Restor Dent Endod.  2020 Nov;45(4):e52. 10.5395/rde.2020.45.e52.

Cytotoxicity and biocompatibility of high mol% yttria containing zirconia

• Sathi Kazi GA
• Yamagiwa R

• KMID: 2512043
• DOI: http://doi.org/10.5395/rde.2020.45.e52

Abstract

Objectives
Yttria-stabilized tetragonal phase zirconia has been used as a dental restorative material for over a decade. While it is still the strongest and toughest ceramic, its translucency remains as a significant drawback. To overcome this, stabilizing the translucency zirconia to a significant cubic crystalline phase by increasing the yttria content to more than 8 mol% (8YTZP). However, the biocompatibility of a high amount of yttria is still an important topic that needs to be investigated.
Materials and Methods
Commercially available 8YTZP plates were used. To enhance cell adhesion, proliferation, and differentiation, the surface of the 8YTZP is sequentially polished with a SiC-coated abrasive paper and surface coating with type I collagen. Fibroblast-like cells L929 used for cell adherence and cell proliferation analysis, and mouse bone marrow-derived mesenchymal stem cells (BMSC) used for cell differentiation analysis.
Results
The results revealed that all samples, regardless of the surface treatment, are hydrophilic and showed a strong affinity for water. Even the cell culture results indicate that simple surface polishing and coating can affect cellular behavior by enhancing cell adhesion and proliferation. Both L929 cells and BMSC were nicely adhered to and proliferated in all conditions.
Conclusions
The results demonstrate the biocompatibility of the cubic phase zirconia with 8 mol% yttria and suggest that yttria with a higher zirconia content are not toxic to the cells, support a strong adhesion of cells on their surfaces, and promote cell proliferation and differentiation. All these confirm its potential use in tissue engineering.

Keyword

Zirconia; Yttria; Biocompatibility; Cellular activity

Figure

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  Figure 1 (A) X-ray diffraction patterns of zirconia before and after heat treatment. All X-ray diffraction peaks are comparable with the standard data of the pure cubic phase containing ZrO2. (B) SEM showed the microstructure of zirconia plates. All coating groups showed collagen coating along with the polished line. The sample without any polishing and coating showed a typical feature pattern of larger grains consisting of clusters of smaller grains (scale bar: 10 µm; arrow and arrowhead: grinding line). (C) Characterized the topography of the zirconia with or without coating using 3-dimensional laser microscopy (scale bar: 100 µm). (D and E) Graph depicting the quantification of the surface roughness Ra (μm) and Rz (μm) of all zirconia samples.SEM, scanning electron microscopy.*p ≤ 0.05; †p ≤ 0.001.

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  Figure 2 (A) Water CA images with or without coating/polishing zirconia surface. (B) CA measurement of samples with or without coating/polishing. (C) Fluorescent staining of L929 cell cultures of the cubic phase containing zirconia with or with coating/polishing in the different time intervals (a-f: 2 hours after seeding; g-l: 3 days; m-r: 7 days) (scale bar: 100 µm). (D) Graph depicting the numbered cell proliferate in different zirconia plates.CA, contact angle.*p ≤ 0.05; †p ≤ 0.001.

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  Figure 3 (A) Alizarin red staining of the BMSCs cultured on zirconia plates up to 28 days (scale bar: 100 μm). (B) Quantify the mineralized area using Image J and data plotted in a bar graph.BMSC, bone marrow-derived mesenchymal stem cell.*p ≤ 0.05; †p ≤ 0.001.

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